Preprints  

We conducted a preliminary study using a synchrotron light source to produce elemental maps, including oxidation states, with spatial resolution <1 µm of individual K-feldspar grains previously used in luminescence dating. The elemental fingerprint that characterised grains with a signal suitable for infrared-radiofluorescence dating had high concentrations of K, Pb and Ba and low proportions of Fe and Ca. In contrast, grains with high Fe and Ca levels yielded an unexpected curve shape.

We describe a new, fully automated extraction system for in situ ¹⁴C at PRIME Lab that incorporates more reliable components and designs than our original systems. We use a LiBO₂ flux to dissolve a quartz sample in oxygen, after removing contaminant ¹⁴C with a lower-temperature combustion step. Experiments with new Pt/Rh sample boats demonstrated reduced procedural blanks, and analyses of well-characterized intercomparison materials tested effects of process variables on ¹⁴C yields.

The island of Patmos is situated in the Southern Aegean Sea (Greece), just north of the present locus of active volcanism. The island is almost entirely build of volcanic rocks, which are 6.6 to 5.2 million years old. We obtain these ages with ⁴⁰Ar/³⁹Ar dating technique on sanidine and biotite minerals. Our new age data indicates a geologically brief volcanic period (lasting less than 1.5 million years) which can be divided in three distinct volcanic intervals and can be correlated to tectonics.

As a result of increasing precision and accuracy in geochronology, interpreting complicated age spectra has become increasingly important, since individual mineral ages often do not directly date the actual geologic process of interest. Here we propose a method for estimating the age of eruption or deposition of a set of minerals dated by the U-Pb system which, in contrast to previous approaches, remains accurate even when the dated minerals have experienced loss of the daughter product Pb.

Reliable chronologies lie at the base of paleoclimatological reconstructions. When working with marine sediment core, the most common dating tool for recent sediments is radiocarbon, but this requires calibration to convert to calendar ages. This calibration requires knowledge of the marine radiocarbon reservoir age and this is known to vary in space and time. In this study we provide 92 new radiocarbon measurements to improve our knowledge of the reservoir age around Greenland.

The mineral zircon is widely used to determine the age of rocks based on the radioactive decay of U to Pb, but the measured U-Pb date can be too young if the zircon loses Pb. We present a new method for estimating the distribution of apparent Pb loss by mathematical convolution. Applying this approach to 10 samples illustrates contrasting patterns of apparent Pb loss. This study highlights the importance of quantifying Pb loss to better understand its potential effects on zircon U-Pb dates.

This study presents the results of an outdoor flume experiment to evaluate the effect of turbidity on the bleaching of fluvially transported sediment. Our main conclusions are that even small amounts of sediment lead to a substantial change in the intensity and frequency distribution of light within the suspension and that flow turbulence is an important prerequisite for bleaching grains during transport.

The marine reservoir age (MRA) that is the difference between the ¹⁴C age of the ocean and that of the atmosphere at a given time. In geochronology, knowing the local MRA is important to derive accurate calibrated ages for ¹⁴C-dated marine material. However, MRA values for coastal West Africa are scarce. From the ¹⁴C-dating of know-age bivalves from Museum collections, we calculated MRA values and populated the MRA dataset for coastal West Africa over a latitdinal transect from 33° N to 15° S.

The carbonate wall deposits of the Trou du Renard Cave (France) were dated using a multimethod approach: U-Th dating by bulk dissolution of samples and ICPMS, U-Th dating by laser ablation ICPMS imaging and radiocarbon dating. The sample compositions were studied to ensure that they can give reliable ages. Ages ranging from 187.9 ± 5.3 ka and 1.4 ± 0.1 ka were found. This approach should make it possible to establish more robust chronologies of archaeological caves.

Radiocarbon dating is a widely used tool to establish chronologies for sediment records. We show that modern aquatic plants in the Laguna del Peinado lake system (Altiplano-Puna Plateau) give too old ages caused by reservoir effects from the input of old groundwater and volcanic CO₂. Our results reveal a spatial variability of the modern reservoir effect within the lake basin, which has implications for radiocarbon-based chronologies in paleoclimate studies in this region and similar settings.

The U–Th–He method is a technique to determine the cooling history of minerals. Traditional approaches to U–Th–He dating are time consuming and require handling strong acids and radioactive solutions. This paper presents an alternative approach in which samples are irradiated with protons and subsequently analysed by laser ablation mass spectrometry. Unlike previous in-situ U–Th–He dating attempts, the new method does not require any absolute concentration measurements of U, Th, or He.

Here, we present the lighting setting implemented in the new Luminescence Dating Research Laboratory at Stony Brook University, USA. First, we performed spectral measurements on different light sources and filters. Then, we measured the loss of signal in quartz and feldspar samples when exposed to various light sources and durations. Finally, our lighting setting is suitable for a luminescence darkroom laboratory, it is simple, inexpensive to build, and durable.

Cosmogenic nuclides like ¹⁰Be are rare isotopes created in rocks exposed at the Earth’s surface and can be used to understand glacier histories and landscape evolution. ¹⁰Be is usually measured in the mineral quartz. Here, we show that ¹⁰Be can be reliably measured in the mineral pyroxene. We use the measurements to determine exposure ages and understand landscape processes in rocks from Antarctica that do not have quartz, expanding the use of this method to new rock types.

Volcanic ash layers are a common tool to synchronize records of past climate, and their estimated age relies on external dating methods. Here, we show that the chemical composition of the well-known, 12000 year-old Vedde Ash is indistinguishable with several other ash layers in Iceland that are ~1000 years younger. Therefore, chemical composition alone cannot be used to identify the Vedde Ash in sedimentary records.

We report aspartic and glutamic acid racemization analyses on Neogloboquadrina pachyderma and Cibicidoides wuellerstorfi from the Arctic Ocean (AO). The rates of racemization in the species are compared. Calibrating the rate of racemization in C. wuellerstorfi for the past 400 ka allows the estimation of sample ages from the central AO. Estimated ages are older than existing age assignments (as previously observed for N. pachyderma), confirming that differences are not due to taxonomic effects.

The Great Unconformity represents an enormous amount of time lost from the sedimentary record. Its origin is debated, in part, due to different approaches used to interpret zircon (U–Th)/He ages. This thermochronometric system is ideal for this problem because the temperature sensitivity varies according to radiation damage. Here we explore the uncertainty associated with the radiation damage model and show how this limits our ability to resolve the origin of the Great Unconformity.

We proposed a new non-destructive mineralogical methodology on inframilimetric grains that allows to quantify the hematite and goethite content and hematite/goethite ratio of grains prior to (U-Th)/He geochronological analysis. (U-Th)/He data performed on different aliquots with different acquisition time shows no remarkable differences in age, opening a new way to investigate the (U-Th)/He data evolution in supergene lateritic duricrusts.

Paleomagnetic data from Cascade Lake (Brooks Range, Alaska) extend the radiometric-based age model of the sedimentary sequence extending back 21 kyr. Correlated ages based on prominent features in paleomagnetic secular variations (PSV) diverge from the radiometric ages in the upper 1.6 m, by up to about 2000 years at around 4 ka. Four late Holocene cryptotephra in this section support the PSV chronology and suggest the influence of hard water or aged organic material.

Prehistoric volcanic eruptions are often dated by wiggle matching series of radiocarbon ages on tree rings to standard calibration curves, ignoring potential contamination by 'old' carbon given off by the volcano. We modeled the effects of low amounts of contamination on wiggle match dates for the 10th century Changbaishan eruption and found evidence of contamination in all. We propose a new protocol to identify the presence of contamination, and provide more secure dates for major eruptions.

The timing and duration of fluid activity within a gold deposit enables a greater understanding of how the deposit evolved and thus help future mineral exploration. This research uses high resolution dating methods to unravel the overprinting fluid activity at the Martabe gold field in Sumatra. Methods outline in this report can be applied to deposits globally.

Potassium-based geochronology, including the ⁴⁰Ar/³⁹Ar and K-Ar methods, provides critical constraints on the timing and duration of many events and processes in earth history. These methods assume that a key parameter, the fraction of potassium with a mass of 40, does not vary in some relevant materials. Some recent work has identified some variability in these materials. This work examines the effects of this variability on calculated K-Ar and ⁴⁰Ar/³⁹Ar ages.